Testing transformers, &amp; c.



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No. 659,656. Patented Oct. I6, |900.

A. REVEREST. TESTING TBNSFORMERS, 81.6.

(Application filed June 25, 1898.)

(No` Model.) 2 Sheets-Shee 2.

W ifi/m z/Luf AUGUSTINE R. EvEREST, or LYNN, MASSACHUSETTS, ASSIGNOR ToTHE GENERAL ELECTRIC coMPANY, or NEW YORK.

TESTING TRANSFORIVI ERS, 84C.

SFECEFCATION forming part of Letters Patent N o. 659,656, dated October16, 1900- Application filed dune 25,1898. Serial No. 684.488. (Nomodel.)

To all whom t may concern: A Be it known that L AUGUSTINE R. EVER- EST,a subject of the Queen of Great Britain, residing at Lynn, in the countyof Essex, State of Massachusetts, have invented certain new and usefulImprovements in Testing Transformers, the., (Case No. 741,) of which thefollowing is a Specification.

My invention relates to devices for testing 1o the insulation resistanceof dynamo-electric apparatus, such as armatures, transformers, coils,and the like.

It has for its object to provide a convenient, and preferably-portable,testing set which I5 may operate at any desired potential within thelimits of the apparatus. It comprises, in brief, a transformer, theprimary of which may be connected to mains at ordinary potentials and bysimple change of conneczo tions be adapted to two or more differentpotentials, such as fifty-two or one hundred and four volts, which arepressures commonly used in alternating-current distributions, and asecondary upon the saine core, with such a number of turns and size ofwire as to have induced therein high potentials, in accordance withwell-known principles. The

device as I have embodied it in practice is' designed to employ upon thehigh-potential 3o side differences of potential of ten thousand volts;but ofcourse I am not limited to any particular ratio. Vith thistransformer, which is mounted in a convenient mannerin a box, which boxmay be lled with oil for security, lcombine upon the high-potential sidea spark-gap in shunt to the mains and also convenient terminals by whicha voltmeter may be connected in on the primary or low-potential side. Inoperation the ap- 40 paratus thc insulation of which is to be tested isconnected in a suitable manner upon the high-potential side, and, thesparkgap having been previously adjusted so that the spark will leap atthc desired potential, the current is turned onto the primary and thepotential gradually raised until the spark jumps. This has the effect ofshort-circuiting the apparatus to be tested, so that any excess ofpotential cannot by accident be 5o passed through it. Unlike some otherdevices, the spark-gap acts at the potential for which it has beenadjusted at no load, irrespective of the relation of curren tandelectromotive force in the circuit, so that the inductance of thetransformer under load or of the apparatus which is to be tested willhave no effect upon the potential at which the spark will pass.

The drawings annexed show a testing-set in which my invention has beenembodied, Figure l being a section on the line l l of Fig. 3 ot'such anapparatus; Fig. 2, aside elevation; Fig. 3, a plan with the part abovethe line 3 3 of Fig. l removed; Fig. 4, a perspective of the inclosingbox for the spark-gap, and Fig. 5 a diagram of the circuits.

In Figs. '1, 2, and 3 A is the box, of which B B are the handles. All ofthe apparatus is inclosed within the box, connection being made to thevarious terminals by the bindingposts a b c d upon the outside of thebox. At ef are other binding-posts across the primary circuit forconvenience in connecting in the Volrmeter. (Not illustrated.) Uponblocks C C is supported the core D of the transformer, of which E is theprimary coil and F the secondary or high-potential coil. The secondaryis made of separately-wound 4coils F2 F2, between which are placedseptum FQ of insulating material, after which the coils are connectedup. A connection-board G is provided by which the two windings of theprimary E may be connected in series or multiple, according as theapparatus is used on one hundred and four or fifty-two voltlines. A cockK is provided by which the oil may be readily removed from the apparatusfor transportation. l

In Figs. l, 2, ande the box surrounding the spark-gap L is shown. Thisconsists of a box l, provided with openings l I4, through which thesparkingterminals Z Z' may be observed. These may be approached orseparated by the micrometerscrew Z2, so that the gap L between thepoints mayv be adjusted as may be required. On the bottom of the box arethe plug-terminals m n, by which when the box is lift-ed out thespark-gap is disconnected from circuit. The spark-gap may then beadjusted as required andthe cover set back in place, thus obviating anyrisk from handling the apparatus while the high-potential IOC current isowing.

the current and to adj ust the primary potential, to the binding-post c,and out at the binding-post b. The voltmeter V, as showndiagrammatically, is connected across the mains to the posts a b,additional bindingposts e f being employed, so that it may bedisconnected readily without interfering with the main circuits. If thedottedline connection at the board G is employed, the coils E E areconnected in multiple, so that the apparatus will be adapted forline-cur rent of lower potential. A high potential is thus induced inthe coil F and through the l mains. This difference of potential iscommunicated to the apparatus W to be tested The latter is representeddiagrammatically as a transformer, the primary coil of which isconnected to one line and the secondary to the other, so that theinsulation between the two coils is under strain of ten thousand voltsdifference of potential. The sparkgap L is connected between theplug-terminals 'Il la.

The method of operation is as follows: With the connections as shown inFig. 5, the apparatus to be tested not in circuit, and the voltmeter in(the ratio of transformation being known) the current is turned on andthe volt-meter is brought to a proper indication, such as 52 or 104 inthe cases already used as illustrative. The spark-gap L is then adjusteduntil when the voltrneter stands at its proper indication the spark willjust pass. Current is then turned off and the apparatus to be testet]connected. The voltmeter, it'

desired, may be cut out, although this is unimportant, as it is underonly moderate strain. After the current is again turned on the plates ofthe watermheostat will be gradually approached until the spark jumps atthe gap L. This, as already pointed out, will shortcircuit the apparatusto be tested, which will thus be protected against any excess ofvoltage. As already briefly pointed out in the statement of invention,the sparking-point is unaected by the character of the load.

What I claim as new, and desire to secure by Letters Patent of theUnited` States, is-

l. An insulation-testing device comprising a step-up transformer, anadjustable sparkgap across the secondary terminals, and terminals forthe device to be tested in parallel with the spark-gap, whereby thelatter may short-circuit the dielectric medium of the device to betested at a determinate potential and prevent discharge through thesame.

i 2. The combination of spark-gap terminals of an inclosing caseprotecting the battery from contact with the terminals, connections forthe terminals fixed to the case, and terminal contacts in the maincircuit so arranged that removing the case fromitssupport breaks thecontact and cuts the spark-gap out of circuit.

3. A testing-set comprisingr a transformer with primary and secondarywindings, a spark-gap across the high-potential leads in shunt to theapparatus to be tested, an inclosing box for the spark-gap terminals,and connections fixed to the box by which the spark-gap is cut out ofcircuit when the box is removed from the transformer-case.

4. The combination of a case, a transformer with primary and secondarywindings in the case, terminals connecting the primary winding to thesupply-leads, auxiliary bindingposts in circuit with the main terminals,secondary leads, a spark-gap in shunt to the secondary leads,aninclosing case for the spark-gap, and terminals upon the case registering with lixed terminals upon the transformer-case; the arrangementbeing such that the removal of the spark-gap and its inclosing casebreaks the sh unt-circuit.

In witness whereof I have hereunto set my hand this 23d day of June,1898.

AUGUS'FINE R. EVEREST.

Vitnesses:

DUGALD McKiLLoP, WILLIAM J. VVOOLDRIDGE.

